The present invention relates to a linear pulse motor.
Linear pulse motors provide high performance as reciprocally movable actuator and hence are widely used for feeding devices in various information peripheral devices such as head feeding devices of the electronic printer and photoelectronic reader. Recently there is a strong need for reduction in dimensions and cost of the linear pulse motor as office automation terminals are being reduced in volume and cost. In addition to these requirements reduction in thickness is required for the pulse motor used for feeding the head of the floppy disc drive.
In view of these requirements, one of the inventors as a coinventor proposed a flat-type linear pulse motor in U.S. Pat. No. 4,578,622 (filed: Oct. 20, 1983) entitled "LINEAR PULSE MOTOR", corresponding to Japanese Patent Application Nos. 57-188843, 57-198658 and 58-220238, of which disclosure is hereby incorporated by reference. In this flat-type linear pulse motor, magnetic pole teeth are formed in the pole piece members. Although this flat-type linear pulse motor fairly meets the requirements of reducing volume and thickness thereof, but it is in practice rather hard to form very small pole teeth in the pole piece members.
Accordingly, it is an object of the present invention to provide a linear pulse motor which is fairly easy in forming pole teeth of the pole pieces as compared to the previously proposed linear pulse motor, thus resulting in reduction in cost of manufacturing pole pieces.
With this and other objects in view, the present invention provides a linear pulse motor which includes: a primary magnetic flux generating unit composed of a pair of cores each having a coil wound therearound and pairs of magnetic poles, each pole being provided at either end portion of a corresponding core; and a scale having a row of first teeth formed therein along a direction of relative travel thereof with respect to the magnetic flux generating unit, the scale and the flux generating unit being disposed so that the scale relatively moves with respect to the primary magnetic flux generating unit by generating magnetic flux in gaps formed between the magnetic poles and teeth facing to the magnetic poles. The pole pieces each include a flat magnetic pole piece member having a head portion and a leg portion and are arranged on a plane with each head portion disposed close to head portions of adjacent pole piece members; and the pole pieces comprise a ferromagnetic thin plate bonded to upper faces of the pole piece members, the thin plate being provided in an upper face thereof with pole teeth portions corresponding to the head portions of the pole piece members, each pole teeth portion having second teeth formed at a predetermined pitch in parallel with the first teeth so that the second teeth may face the first teeth.
The second teeth of the thin plate may be land portions formed by parallel slits through the thin plate.
Alternatively, the second teeth may be parallel ridges formed in the thin plate. This thin plate is rather higher in strength of the pole teeth portions and in adhesive strength with respect to the pole piece members than the slit thin plate.
The thin plate may include two pairs of bonded portions, each bonded portion including a second head portion and a second leg portion corresponding to the head portion and the leg portion of the corresponding pole piece member respectively. Preferably, each second head portion of one pair of the bonded portions is integrally connected to the adjacent second head portion of the other pair by a connecting portion which has a thickness smaller than the height of the second teeth. The provision of the thinner connecting portion reduces leakage of magnetic flux.